List Built In Methods

 

Built in Methods for List Class to perform certain operations

There are certain operations can be done on Lists and are built in for List Class .

• append() : append data at the end of exist list.

 #program 

 l1 = [10, 20, 30, 40, 50]
 print("l1 : ", l1)
 l1.append(60)
 print("l1 : ", l1)

 #output

 l1 :  [10, 20, 30, 40, 50]
 l1 :  [10, 20, 30, 40, 50, 60]

• extend() : add all elements of a list to other list.

 #program 

 l1 = [10, 20, 30, 40, 50]
 l2 = [60, 70, 80, 90]
 print("l1 : ", l1)
 print("l2 : ", l2)
 l1.extend(l2)
 print("l1 : ", l1)
 print("l2 : ", l2)


 #output

 l1 :  [10, 20, 30, 40, 50]
 l2 :  [60, 70, 80, 90]
 l1 :  [10, 20, 30, 40, 50, 60, 70, 80, 90]
 l2 :  [60, 70, 80, 90]

• insert() : insert new item/member at given index.

 #program 

 l1 = [10, 20, 30, 40, 50]
 print("l1 : ", l1)
 l1.insert(2, 60)
 print("l1 : ", l1)

 #output
 l1 :  [10, 20, 30, 40, 50]
 l1 :  [10, 20, 60, 30, 40, 50]

• remove() : remove item from list (first occurrence).

 #program 

 l1 = [10, 20, 60, 30, 40, 50, 60]
 print("l1 : ", l1)
 l1.remove(60)
 print("l1 : ", l1)

 #output
 l1 :  [10, 20, 60, 30, 40, 50, 60]
 l1 :  [10, 20, 30, 40, 50, 60]

• pop() : remove and return element at given index.

 #program

 l1 = [10, 20, 60, 30, 40, 50, 60]
 print("l1 : ", l1)
 value = l1.pop(2)
 print("value : ", value)
 print("l1 : ", l1)

 #output

 l1 :  [10, 20, 60, 30, 40, 50, 60]
 value :  60
 l1 :  [10, 20, 30, 40, 50, 60]

• clear() : remove all items from the given list.

 
 #program

 l1 = [10, 20, 60, 30, 40, 50, 60]
 print("l1 : ", l1)
 l1.clear()
 print("l1 : ", l1)

 #output
 l1 :  [10, 20, 60, 30, 40, 50, 60]
 l1 :  []

• index() : return index of 1st match item.

 #program

 l1 = [10, 20, 60, 30, 40, 50, 60]
 print("l1 : ", l1)
 found = l1.index(60)
 print("found at :", found)

 not_found = l1.index(70)        #will throw error if value not found
 print (not_found, "not found")

 print("l1 : ", l1)

 #output

 l1 :  [10, 20, 60, 30, 40, 50, 60]
 found at : 2
 Traceback (most recent call last):
   File "C:/Self_Practice_Er_M_S_Dandyan/Python/Pycharm/xml/main.py", line 8, in <module>
     not_found = l1.index(70)
 ValueError: 70 is not in list

• sort() : sort list items in ascending order.

 #program

 l1 = [10, 40, 60, 30, 20, 50, 60]
 print("l1 : ", l1)
 l1.sort()
 print("l1 : ", l1)

 #output

 l1 :  [10, 40, 60, 30, 20, 50, 60]
 l1 :  [10, 20, 30, 40, 50, 60, 60]

• reverse() : reverse the order of item in given list

 #program

 l1 = [10, 40, 60, 30, 20, 50, 60]
 print("l1 : ", l1)
 l1.reverse()
 print("l1 : ", l1)

 #output

 l1 :  [10, 40, 60, 30, 20, 50, 60]
 l1 :  [60, 50, 20, 30, 60, 40, 10]

• copy() : return shallow copy of the list.

 
 #program

 l1 = [10, 40, 60, 30, 20, 50, 60]
 print("l1 : ", l1)
 l2 = l1.copy()
 print("l2 : ", l2)

 #output

 l1 :  [10, 40, 60, 30, 20, 50, 60]
 l2 :  [10, 40, 60, 30, 20, 50, 60]

• count() : return the number of elements with specified values

 #program

 l1 = [10, 40, 60, 30, 20, 50, 60]
 print("l1 : ", l1)
 count = l1.count(60)
 print("count", count)
 print("l1 : ", l1)

 #output

 l1 :  [10, 40, 60, 30, 20, 50, 60]
 count 2
 l1 :  [10, 40, 60, 30, 20, 50, 60]

Example on few Python Built in Methods on LIST 

 #program

 l1 = [10, 40, 60, 30, 20, 50, 60]
 print("l1 : ", l1)
 print("sum(l1) : ", sum(l1))    # will return sum of all elements in List
 print("max(l1) : ", max(l1))    # will return maximum value in list
 print("min(l1) : ", min(l1))    # will return minimum value in List
 print("len(l1) : ", len(l1))    # will retunn total members count in List

 #output
 l1 :  [10, 40, 60, 30, 20, 50, 60]
 sum(l1) :  270
 max(l1) :  60
 min(l1) :  10
 len(l1) :  7